Magnetically delayed arming device for a fuze



April 11, 1961 R. BIANCHI 2,978,982

MAGNETICALLY DELAYED ARMING DEVICE FOR A FUZE Filed Sept. 23, 1953 2Sheets-Sheet 1 FIG.2. zl 1 16. 3. 2|

INVENTOR RENATO BIANCHI- 'ATTORNEYS April 11, 1961 R. BIANCHI 2,978,982

MAGNETICALLY DELAYED ARMING DEVICE FOR A FUZE Filed Sept. 25, 1953 2Sheets-Sheet 2 INVENTOR RENATO BIANCHI ATTORNEYS MAGNETICALLY DELAYED AGDEVICE FOR A FUZE Renato Bianchi, Laurel, Md., assignor to the UnitedStates of America as represented by the Secretary of the Navy FiledSept. 23, 1953, Ser. No. 382,015

7 Claims. (Cl. 102-79) (Granted under Title '35, U.S. Code (1952), sec.266) The invention described herein may be manufactured and used by orfor the Government of the United States of America for governmentalpurposes without the payment of any royalties thereon or therefor.

The present invention relates to a fuze and more particularly to adelayed arming device for a fuze adapted for use in various types ofordnance missiles such, for example, as both small and large caliberprojectiles.

Prior art delay arming devices such, for example, as the type employingrotors actuated to an armed position in response to frictional andinertia forces and the type actuated by escapement devices have notproven entirely satisfactory for the reason that the devices dependingupon the aforesaid forces have not given reproduce'able results andsufiicient time delay periods to meet the desired requirements and theescapement devices often times being erratic in operation due to thefaulty functioning of the delicate and intricate mechanisms thereof.

In view of the foregoing, the present invention contemplates theprovision of a new and improved rotor device for a fuze adapted toovercome the objectional characteristics heretofore encountered in priorart devices of this type by providing simpleand efficient damping meanswhich delays the movement of the arming rotor from an initial positionto an armed position to meet the desired requirements and which is voidof delicate and intricate mechanisms.

Moreover, the arming device comprises a magnetized ball rotatablysupported within a spherical cavity formed in aconductive housing, theball rotor carrying a detonator and, if desired, suitable centrifugallyactuated locking detents may be employed, to maintain the rotor in aninitial safe position. In response to the spin of the projectile,however, the rotor is adapted to be moved from an unarmed position to anarmed position. In accordance with the present invention, however, asthe ball moves toward an armedposition in response to centrifugal forceeddy-currents are induced in the conductive casing in response to suchmovement. These eddy-currents create a force proportional to therelative velocity of the rotor and casing which opposes the forcetending to move the rotor thus retarding the movement of the rotor to anarmed position. When the rotor has been moved to an armed position, thedetonator is in alignment with the percussion primer and the lead-incharge and provides a continuous firing train from the primer to theusual booster charge mounted in the fuze casing, the explosive chargesbeing fired in successive. order as the firing pin is forcibly driveninto engagement with the aforesaid primer. 7

An object of the present inventionis to provide anew and improveddelayed arming device for a fuze.

. Another object of the invention is the provision of a' magneticdamping means for delaying" the arming of a projectile fuze.

Still anotherobject of the invention is the provision of a new andimproved magnetic damping device wherein an arming rotor'is subjected toadamping action as'the Patented Apr. 11, 196.1

rotor is rotated in a conductive casing thereby to prevent prematurearming of a fuzed projectile.

A still further object of the-invention of a new an improved magneticdamping device for a fuze which is economical to manufacture, reliablein operation and which possess all the qualities of durability inservice.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

Fig. l is a longitudinal section of a fuze illustrating a preferredembodiment of the present invention arranged therein with the armingrotor thereof in an unarmed position;

Fig. 2 is a view in diagrammatical form of the delay device of Fig. 1with the ball arming rotor thereof in an unarmed position; 1

Fig. 3 is a view similar to Fig. 2 with the device in an armed position;V i

Fig. 4 is a longitudinal sectional view of a fuze illustrating analternate arrangement of the present invention;

Fig. 5. is a view in diagrammatical form of arrangement of the device ofFig. 4 with the cylindrical rotor thereof in an unarmed position; and IFig. 6 is a view similar to Fig. 4 with the rotor in armed position.

Referring now to the drawings and more particularly to Fig. 1 thereof,the numeral 10 generally indicates a fuze comprising, a casing 11threaded as at 12 for attachment to an explosive shell. The casing 11 isprovided with a centrally disposed bore 13 terminating in a restrictedbore '14. Bore 13 is threaded as at 15 for threaded engagement with acontainer 16 having a booster charge 17 arranged therein and bore 14having an impact responsive firing pin 18 releasably supported thereinby a support 19.

The device of the present invention is arranged within the bore 13 andis generally indicated by the reference character 21. The aforesaiddevice comprises a magw netized casing 22 composed of any siutableelectroconductive paramagnetic material such, for example, as iron orthe like and having a spherical cavity or recess 23 formed therein. Thecavity 23 communicates with a well 24 formed in the casing 22 at one endthereof and with a bore 25 formed in the other end thereof, The well 24is threaded as at 26 for threaded engagement with a plug or retainingelement 27. The bore 25 has arranged therein a percussion primer 28 inalignment with the firing pin 18 and a lead-in charge 29 disposed withina bore 31 formed in the plug 27, the charge 29 being in engagement withthe booster charge 17.

A magnetized spherical rotor 32 is rotatably supported within thespherical recess 23 of the casing 22 and a complementary sphericalrecess 33 formed in the plug 27, the ball being adapted to be rotatedfrom an initial safe position, Fig. 1, to an armed position, Fig. 3, asthe rotor is moved in response to centrifugal force during the spin ofthe projectile along its trajectory. The ball rotor 32 is provided witha-centrally disposed bore 34 extending therethrough in which is arrangeda detonator 35 normally out of alignment with the foresaid primer whenthe rotor is in the initial safe position, Figs. 1 and 2. It will benoted that the ball 32, Fig. 2, is arranged within the rotor casing 22with the magnetic south pole on the rotor disposed opposite the magneticnorth pole on the casing and the magneticnoith pole on the rotordisposedoppositc the magnetic south pole on the casing.

Thus by this arrangement, the rotor is initially mainrotor in an initialsafe position and to release the rotor for rotation to an armedposition, may be omitted.

It will be understood, however, that as the missile spins along itstrajectory the rotor 32 is rotated within the aforesaid sphericalrecesses in response to centrifugal force. Such movement of the rotorwithin the conductive casing assembly induces eddy-currents and theseeddy-currents create an electromagnetic force, proportional to therelative velocity of the members, opposing the centrifugal force tendingto move the rotor from an initial safe position to an armed positionthus re tarding the rate of movement of the rotor. While the aforesaiddevice has been described in connection with a magnetized rotor disposedwithin a magnetized casing as illustrated, it will be understood thatthe same results may be obtained by employing a non-magnetized rotordisposed within a magnetized casing or by having the rotor magnetizedand casing non-magnetized. 7

Referring now to an alternate arrangement ofthe device illustrated inFigs. 4 to 6 and more particularly to Fig. '4 thereof, the numeral 38generallyindicates the rotor device. The device is arranged in the fuzehousing 40 and comprises a casing 41 composed of suitable conductivematerial such, for example, as iron or the like and having arrangedtherein a rotor support or base 42 for rotatably supporting a magnetizedwafer or disc type arming rotor 43 as by a shaft 44 carried thereby. Inthis arrangement it will be noted that the rotor 43 is maintained in aninitial safe position by a pair of oppositely disposed centrifugallyactuated detents 46 disposed within a pair of notches, respectively,formed in the rotor. The detents are pivotally mounted on the base 42 asat 47, each detent being maintained in engagement with the notches by aspring 48.

As the projectile is fired from a gun and during the angularacceleration thereof the inertial force of the rotor moves the rotorangularly sufficiently to disengage the detents from the notches and towind at torsional spring 49 secured to the rotor and base. When theangular acceleration of the projectile has disappeared and before thedetens are returned to an initial position by the springs, the spin ofthe projectile is sufiicient to maintain the detents in a releaseposition with the detents out of engagement with the notches. With thedetents out of engagement with the notches the arming rotor is free tobe rotated to an armed position by the aforesaid torsional spring 49. Itwill be understood, however, that the rotor is first moved in onedirection to a release position by the inertial force thereof inresponse to the initial angular acceleration of the projectile andthereafter moved in a reverse direction to an armed position, Fig. 6, bythe spring 49.

When the rotor 43 is in the initial safe position, Fig. 5, it will benoted that the detonator 51 carried thereby is normally out of alignmentwith the electroresponsive detonator 52 mounted in the base 42. Uponrelease of the rotor, however, the rotor is moved to an armed position,Fig. 6, in the aforesaid manner with the detonator 51 in alignment withthe detonator or primer 52 and the rotor locked in the armed position bythe aforsesaid detent and notch arrangement.

Furthermore, when the rotor moves to an armed position the detonator 51in the rotor moves into alignment with a lead-in charge 55 arranged inthe casing 41 in engagement with a booster charge 57 and'thus a continuous explosive train is provided from the detonator 51 to the boostercharge 57.

The movement of the rotor to a release position and to an armed positionis controlled by a stop pin 58 carried by the rotor and disposed in asubstantially semicircular slot 59 formed in the base 42, Figs. and 6.

It will be understood, however, that during the rotation of themagnetized rotor 43 within the conductive casing 41 by the action ofspring 49, eddy-currents are induced in the casing and theseeddy-currents create a force retarding the rotor thereby delaying thearming of the fuzed projectile.

Furthermore, the aforesaid device is particularly adapted to use inconnection with electric control fuzcs such, for example, as the typewhich fire in response to an electrical impulse generated or a voltagedischarged from a storage device as the projectile strikes the target orthe type which fires in response to an electrical impulse inducedtherein when the projectile is in proximate relation with respect to thetarget.

In view of the foregoing, it will be apparent that a new and improveddelayed arming device has been devised for use with an ordnance missile.wherein magnetic damping means are provided for retarding the movementof the arming rotor thereof from an initial position to an armedposition and which is economical to manufacture, reliable in operationand which possesses all thc qualities of durability in service.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. A delayed arming device for a spin projectile com prising a casingcomposed of magnetic material having north and south magnetic poles in aplane normal to the axis of spin of the projectile, a magnetic rotordisposed within said casing and having north and south poles alignedwith and in opposition with the magnetic poles on said casing formaintaining the rotor in an initial safe position in response to themagnetic flux therethrough, said rotor being adapted to be moved fromsaid initial safe position to an armed position in response tocentrifugal force, the movement of the magnetic rotor within saidmagnetic casing inducing eddy-currents to retard movement of the rotorfrom said initial position to said armed position.

2. A delayed arming device for a spin projectile comprising acasingcomposed of conductive material, a magnetic rotor movable withinsaid casing, means for locking said rotor in an initial safe positionand for releasing the rotor for rotation to an armed position as therotor is moved a predetermined amount to'a release position in responseto the initial angular acceleration of the projectile as the projectileis fired from a gun, resilient means operatively connected to said rotorfor rotating the rotor from said release position to an armed positionwhen the spin of the projectile has decreased to a predetermined value,the movement of said rotor from said release position to said armedposition being retarded by the eddycurrents induced in response to therotation of said magnetic rotor within said conductive casing.

3. A delayed arming device for a spin projectile Oil1- prising a casingcomposed of conductive material, a magnetic rotor normally locked withinsaid casing in an initial safe position and moved to a release positionin response to the initial acceleration of the projectile as theprojectile is fired from a gun, means responsive to centrifugal forcefor locking said rotor in said initial position and for releasing therotor for rotation from said initial position to an armed position asthe locking means is moved to a release position by said force,resilient means operatively connected to the rotor for rotating therotor from said release position to an armed position, said movement ofthe magnetic rotor within the conductive casing inducing eddy-currentsto retard rotation of the rotor from said release position to said armedposition, and means on said locking means for urging the locking meansinto locking engagement with'the rotor as the spin of the projectilereaches a predetermined value and the rotor is in said armed position.

4. A delayed arming device for a spin projectile comprising a. casingcomposed of 'magnetic material and magnetically poled in a plane normalto the axis of spin of the projectile, and a movable magnetically poledele ment disposed within said casing and yieldably held in a safeposition by magnetic attraction between the poles thereof and the polesof said casing, said element being dynamically constructed to be movedfrom an initial safe position to an armed position in response tocentrifugalforce during the flight of the projectile, the movement ofsaid element being retarded by eddy-currents induced therein during suchmovement.

5. A delayed arming device for a spin projectile comprising a casingcomposed of magnetic material and having a seat therein, a bipolarmagnetized element disposed Within said seat in engagement with saidcasing and of dynamic structure to effect movement thereof in responseto centrifugal force, said element being yieldably retained in aninitial safe position by magnetic attraction between the poles of saidelement and the casing and adapted to be moved therefrom to an armedposition by centrifugal force during the flight of the projectile, therate of movement of the element being retarded by eddycurrents thereincaused by said movement.

6. A claim according to claim 5 and including means I 6 l K formaintaining the element within said seat in engagement with the casing.

7. A delayed arming device for a spin projectile comprising a casingcomposed of magnetic material and having a spherical cavity therein, aspherical bipolar magnetized rotor disposed within said cavity inengagement with said casing and dynamically constructed for movement bycentrifugal force from an initial safe position to an References Citedin the file of this patent UNITED STATES PATENTS Flather Sept. 12, 1916McCaslin Feb. 24, 1948

